sambacc: make config module robust to unexpected jsonschema versions

If jsonschema module doesn't understand our schemas then we assume that
the version is too old and we should treat it the same as not having
jsonschema installed. We recently found that having older jsonschema
versions present in the container actually breaks sambacc. Because we
prefer to install from rpm packages rather than pip in samba-container
we ended up with older, and an untested version, of the library. This
change tries to make the sambacc code more robust in that case.

Signed-off-by: John Mulligan <[email protected]>

Author: phlogistonjohn

sambacc/config.py

@@ -52,11 +52,19 @@ class ValidationUnsupported(Exception):
     pass
 
 
+class _FakeRefResolutionError(Exception):
+    pass
+
+
 def _schema_validate(data: dict[str, typing.Any], version: str) -> None:
     try:
         import jsonschema  # type: ignore[import]
     except ImportError:
         raise ValidationUnsupported()
+    try:
+        _refreserror = getattr(jsonschema, "RefResolutionError")
+    except AttributeError:
+        _refreserror = _FakeRefResolutionError
 
     global _JSON_SCHEMA
     if version == "v0" and version not in _JSON_SCHEMA:
@@ -66,7 +74,10 @@ def _schema_validate(data: dict[str, typing.Any], version: str) -> None:
             _JSON_SCHEMA[version] = sambacc.schema.conf_v0_schema.SCHEMA
         except ImportError:
             raise ValidationUnsupported()
-    jsonschema.validate(instance=data, schema=_JSON_SCHEMA[version])
+    try:
+        jsonschema.validate(instance=data, schema=_JSON_SCHEMA[version])
+    except _refreserror:
+        raise ValidationUnsupported()
 
 
 def _check_config_version(data: JSONData) -> str: